1. Field of the Invention
The invention relates to movement along a tubular passage, and more particularly to a pressure actuated means for advancing an elongated flexible member.
2. Description of the Prior Art
Various medical procedures involve the oral or anal introduction of an implement such as an endoscope or drain into an internal body cavity, and the development of suitable fiber optics systems has greatly advanced the effectiveness of endoscopes. However there are difficulties in providing for insertion of elongated elements which must be sufficiently flexible to advance through irregular passages without damaging sensitive tissues yet rigid enough for external manipulation.
U.S. Pat. No. 4,148,307 describes a tubular medical instrument having at least three inflatable cuffs which are inflated in a sequence to move the instrument along a tubular passageway. The cuffs must be specially formed and must engage and distend the wall of the passageway. Furthermore, reliance is placed on substantial displacement of one cuff by another cuff which cannot always be assured, particularly if the wall of the passageway is relatively rigid. Furthermore, during forward movement of the instrument, the passageway is blocked by a cuff rearwardly of the head of the instrument which increases the gas pressure within the passageway if the forward end of the passageway is blocked.
U.S. Pat. No. 2,855,934 describes a similar tubular instrument with only two inflatable sleeves, corresponding to said cuffs, but requires a piston and cylinder assembly within the tube of the instrument. Such an assembly obstructs the tube undesirably and also creates a substantial length of rigid section in the instrument which increases the difficulty of moving the instrument around relatively sharp curves. The instrument is also objectionable because of the increase in gas pressure with forward movement.
A self-propelling, self-locating colonoscope has been described having a bellows intermediate a pair of inflatable bladders which have the objections of the sleeves or cuffs in said patents.